This invention relates to connecting duct liner in a conduit system, and more particularly to a duct liner interconnect device for temporarily interconnecting the ends of two sections of flexible duct liner and for enabling automatic application of lubricant to lightguide cables, wire cables, or the like while they are being pulled into and through the conduit.
It is common practice to run lightguide cables through wiring ducts provided with duct liners located underground. The duct liner is usually installed in sections, typically 800 feet long, and a coupling device is installed at the junction of adjacent duct liner sections to both interconnect the sections and provide a permanent covering for the discontinuity in the duct liner.
In the past, it has been customary to have a man at the intermediate point of the cabling into the duct liner who lubricates the cable as he inserts it into the duct liner so that as the cable is pulled through the duct liner it will not be subjected to damage to its insulation or to stretch damage or possible rupture. In practice, the hands of the men inserting and greasing the cable become greased and slippery and this can set a practical limit on the length of the pull. Moreover, since the spacing between man holes is typically in the order of 800 ft., as the cable is pulled through the duct liner between adjacent man holes, it becomes difficult if not impossible to inject enough lubricant at the insert point for any lubricant to remain on the cable until the leading portion of the cable reaches or approaches the next man hole.
Improvements in the means and methods for pulling electrical wires or cables through duct liner are disclosed in U.S. Pat. No. 3,565,213 entitled LUBRICATING MEANS AND METHOD FOR ELECTRICAL WIRING CONDUITS. This patent discloses coupling devices which permanently couple together the ends of a pair of duct liners, and which are provided with three grease fittings for supplying lubricant under pressure to the duct liner at selected openings which may be as little as ten feet or less apart. The coupling device comprises a sleeve member which is internally threaded and adapted to receive threaded ends of pipe sections of the duct liner. Internal shoulders of the coupling device prevent the entrance of the pipe sections too far into the coupling device to prevent obstruction of the threaded grease fitting opening by any part of the duct liner. After lubrication through the fittings is completed, the grease fittings may be removed and the openings are normally plugged by a removable plug. Although this coupling device facilitates lubrication of cable or wiring contained within a duct liner, during wiring pulls, the coupling device is a permanent part of the duct liner system.